To be able to determine which building a pedestrian can see by the naked eye for any given coordinate is the core of this paper. The project is a part of the SpaceBook project, which caters to help tourists and urban workers in a city environment. Therefore it is important that the program has a tight correspondence to the real world.

Maps are exported from OpenStreetMap and imported into PostGIS, an extension to PostgreSQL. Functions are constructed in PostGIS to determine which buildings are visible from a given GPS-coordinate. Checking the center of the buildings as well as all the corners of said building does this. The program has inherited execution time constraints from the SpaceBook project. These are met for relatively small radius around the pedestrian (500 meter radius).

Optimization of the program is hard to accomplish due to the rather complex building placement in a city. There is no safe assumption of the city environment to be made that can be used to further accelerate the execution time of the program.